This invention relates generally to tools for working concrete and more particularly concerns a multi-purpose concrete working tool which is capable of cutting, consolidating, finishing, and checking concrete slabs to produce a surface on the slab of unusual flatness.
For certain floor installations, it is necessary that the concrete floor or slab be both very flat and very level. For example, in a warehouse where automated or semi-automated stacking systems having long, vertically extending booms are operating on concrete floors, it is necessary that the floor in the aisles of such warehouses be as nearly flat and level as possible. If the concrete floor is not flat, the boom will tip from side to side as the equipment rolls across the uneven concrete surface. Consequently, in that and other applications, it has become necessary to produce floors which are "very flat" or "super flat".
In the 1986 edition of the American Concrete Institute's "Manual of Concrete Practice", Committees 117 (Tolerances) and 302 (Construction of Floors) revised their floor recommendations to embrace the use of "face floor profile numbers" ("F-numbers"). The F-number system of surface definition and control was developed by the Edward W. Face Company of Roanoke, Va. specifically to eliminate the numerous technical and legal problems routinely encountered with conventional straight-edge type tolerances for specifying flatness of concrete floors. The F-number system provides a uniform, rational system for specifying the flatness of a concrete floor.
Two separate F-numbers may be used to define the shape of the worst acceptable localized floor profile. The first F-number, "F(F)", is the flatness number and specifies the localized waviness or curvature of the floor observed in any two-foot section. The second F-number, "F(L)", specifies the localized levelness of the floor by restricting the maximum elevation difference to be observed between two points separated by ten feet. The following equations are used to determine the F-numbers for any specific floor: ##EQU1##
While the range of possible F-numbers theoretically extends from 0 for a very poor surface to infinity for a surface of perfect flatness, the F-numbers of commercial floors usually fall between F-15 and F-45. The F-number scale is linear so that relative flatness of two different floors will be proportional to the ratio of their respective F-numbers. In general the following minimum F(F) numbers define grades of floors:
______________________________________ Minimum F(F) ______________________________________ Not critical 18 Average 25 Better Than Average 35 Very Flat 50 Super flat 100 ______________________________________
Conventionally, a concrete floor is finished by first using a screed to strike off the poured concrete to a predetermined elevation. Once the concrete has been screeded to elevation, a bull float is used to work the fine aggregate (fines) to the surface to produce a uniform, smooth textured surface. While the bull float produces a surface that is smooth in texture, as opposed to being abrasive, the bull float does not remove localized waviness in the surface, and in fact, may produce such waviness, thereby lowering the F-number of the surface. Once the surface has been worked by the bull float and the concrete has hardened to some degree, a power float is used to further smooth the texture of the surface. After the surface has been worked by the power float, a power trowel is used to further smooth the texture of the surface. The result of the bull float, power float, and power trowel is to provide a surface that is smooth in texture but yet may have a high degree of waviness, and consequently a low F-number indicating lack of flatness.
With the advent and adoption of the F-numbers for specifying and defining flatness for concrete floors and with the demand for very flat and super flat floors for certain critical installations, it has become necessary to provide a means for finishing the surface of a concrete slab to a high degree of flatness.
The prior art has not specifically addressed the problem of finishing a very flat or super flat floor. The Haivala U.S. Pat. No. 3,082,460 discloses a concrete working tool (paver's edge) which has an elongated hollow straight edge, ten or twelve feet long, with an elongated handle attached to it. The straight edge is lightweight and has a V-shaped leading edge and is primarily useful for checking the flatness of a finished surface. While the Haivala patent suggests that the tool can be used to strike off or cut concrete as well as check, the light weight of the tool and the inability to adjust the pitch of the edge remotely by the operator over a continuous and wide range of angles make the Haivala tool particularly unsuitable for any work other than very light finishing or checking.
The Tullis U.S. Pat. No. 1,952,398 also discloses a paver's edge with a straight edge set at a fixed angle to the handle. Consequently the angle of the straight edge cannot be varied over a sufficient range of angles to allow the tool to be used to strike off and consolidate a concrete surface. Moreover, the rounded edges of the straight edge will tend to float or ride up on high spots thus sacrificing accuracy during striking off of the concrete. The lack of pitch adjustment for the edge with respect to the concrete surface also means that the edge cannot be pushed to the center of the slab, but instead must be lifted to the center of the slab, thereby limiting the tool's weight to about 15 pounds or less.
A number of patents including Paine et al. U.S. Pat. No. 4,335,485, Irwin et al. U.S. Pat. No. 3,798,701, Maggio et al. U.S. Pat. No. 4,520,527, Chiuchiarelli U.S. Pat. No. 3,146,481, Ferrell et al. U.S. Pat. No. 3,090,066, Bennett U.S. Pat. No. 2,934,937, Freeman U.S. Pat. No. 2,834,199, Abram U.S. Pat. No. 1,590,342, Peterson U.S. Pat. No. 3,729,765, and Lapham U.S. Pat. No. 2,999,261, disclose bull floats or trowels with remotely adjustable pitch. Such devices cannot, however, strike off, consolidate, and check a concrete floor to produce an unusually flat surface.